Propyl nitrate monofuel and method of use with nickel salts



United States Patent PROPYL NITRATE MONOFUEL AND. METHOD OF USE WITHNICKEL SALTS Charles H. King, Jr., Manchester, Conn., assignor to UnitedAircraft Corporation, East Hartford, Conn, a corporation of Delaware NoDrawing. Application October :11, 1954 Serial No. 461,645 1 14 Claims.(Cl. 60-3544) The present invention relates to an improved monofuel ormono-propellant for reaction motors, rockets, jetpropulsion motors, aswell as other jet-propelled devices.

The term jet-propulsion devices, as used herein, relates to deviceswhich derive their driving power from the escape through a jet or nozzleat relatively high velocy of the mass comprisingth p oduct .v esult nfrom a combustion or exothermic decomposition of a fuel. The jet may beexhausted into the open air as in the rocket type of device, or it maybe directed on a movable object as in the turbine type of device.

Propyl nitrate is known to be a useful monofuel or mono-propellant forjet-propulsion devices as evidenped by the prior patent to Doumani-et.al,. 2,- 6 4 s07'9. The term propyl nitrate as used herein relates .toboth normal propyl nitrate and isopropyl nitrate which are chemicalisomers. 1 n using .propylnitrate as 'a monofuel," as for example, in ajet-propulsion motor, it is charged into a feed tank and pressured withan inert gas, such as nitrogen. The fuel ispre'ssured'lbythe inert gascontained in a second tank under high pressure, as for example, 15002,914,910 Patented Dec. 1, 1959 f ce as a slurry would also bedisadvantageous as the presence of the catalytic metal surface wouldtend to make e affected during storage and in the feed lines to thecombustion chamber.

Examples of suitable nickel salts which may be used in accordance withthe present invention are nickel: car,- bonyl, nickel acetyl acetonate,nickel diisopropyldithiocarbarnate and nickeldinormalpropyldithiocarbamate.

Generally, the salt, calculated as metallic nickel, is in an amount from0.02 to 1.0 percent by weight of the propyl nitrate and preferably from0.1 to 0.25 percent by Weigh Compa t ve. een condu w ich ow he 1LlPIiQresult obtained by the addition of a soluble p.s.i., through suitablelines and a pressure reducing control valve. The pressured propylnitrate is then released from the fuel tank and fed through suitablelines andcontrol valves through an ejector or atomizer into a combustionchamber. In the combustion chamber, the propyl nitrate is ignited bysuitable means and-allowed to decompose or burn.

The paramount disadvantage'of gpropyl nitrate as a monofuel is that alarge combustioncharriber isrequred to decompose it. This isundesirable, particularly in .air-

craft, where'lightnessflin weight 'is so essential and avjail- 1 ableSpace is often at a premium. I I,

An obj ct of my invention is to provide c aly c means whereby'a smallercombustion chamber may be employed for decomposing-prqpyl nitrate thanfhashereinvention to provide catalytic means to improve the .startingcharacteristics and combustion efficiency of propyl nitrate as amono-propellant,

"I have discovered that the foregoing objects may. be

accomplished by the additiontopropyl nitrate of a soluv.tof ore beenpossible. .It is also a ,further object ,of my ticles in the combustionchamber bymerely.feeding nickel particles from an outside ,line to thecombustion chamber sincethis would require a .mechanism to injectanddis- :perse a streamof metal particles .inthe combustion cham- =b.eragainst .the .high combustion :pressure. -Merely intro'duci'ng' 'the'metal particles v a,nd .the propyl ,riitrate' f uel :nickel saltcompared to pure propyl nitrate'or for propyl nitrate with salts ofother metals as shown in Table 1. For example, there is an increase ofspecific impulse .(lsp) to 167 sec. when normal propyl nitrate,containing 0.725 percent nickel carbonyl by weight (0.25 percent Ni) isdecomposed in a chamber with ac'haracteristic length (11*) or 430 inchescompared to marginal operation at a specific impulse at 145 sec. for thesame chamber using pure normal propyl nitrate. Since 51 67 see. is thetheoretical specific impulse for the test conditions-a chamber pressureof 300 p.s .i. and normal atmospheric pressure exhaust, this correspondsto an increase in combustion efliciency from 87 to Since thisconcentration of nickel carbonyl in normal-p opyl n rat else Produced eent a ly 109% combustion efliciency when the characteristic length i(L*) of the combustionchamber was'reduced to 315 inches, further.reduction in characteristic .length'is obtainable using thiscatalyst-fuel mixture. The characteristic length L* is the ratio of thecombustion chamber volume to the exhaust nozzle throat area inconsistent throat area in consistent units and is a measure of thevolume required for combustion which is essentially unaffected by thescale of the rocket or combustion chamber. The particular tests relatedwere accomplished using cylindrical combustion chambers of approximately401135; thrust requiring a fuel flow of about 0.25 lb. of propyl nitrateper sec. The combustion chamber with a characteristic length of 430inches was 3 inches in diameter and 5 /2 inches long and exhaust-nozzlethroat area was approximately 0.09 sq..in. Additional tests in Table Iwere accomplished in a chamber identical in cross section and throatarea but only 4 inches long (L*=3l5 inches).

The results obtained by using the soluble nickel salts are not onlyadvantageous but are surprising. For example, chromium acetylacetonate,which is an effective catalyst for the decomposition of asimilar mono-propellant, namely, ni'tromethane, did not increase therate of decomposition of normal propyl nitrate as shown in Table I. i

In order to describe my invention even further, data on thedecomposition of normal propyl nitrate' containing four different nickelsalts ,are presented in Table I. As can be seen, specific impulse andcombustion efficiency were increased from 4.2 to 20.2% by the additionof .varying amounts of these salts. v i '7 In addition, to show that allmetal salts do not "have the same desirable catalytic effect on thedecomposition of normal propyl nitrate, further data are presented inTable I. These data show that salts of iron, lead, cobalt On the otherhand, with the nickel salt Table I Chamber Com- Metal in lap lap with Cwith Percent L in. pound in Solution Without Without Oom- Com IncreaseSolution pound pound l 315 0.21 0. 048 144 3, 310 153 3. 520 6. 2 NwkelAmyl Acemnate 315 0. 44 0. 141 3,240 153 a. 520 7. s Nickeldlisopropyldlthlooarbamate g: g: 32 g: fig g 2: Nickeldlnormalpropyldithiocarbamate- 315 1. 05 0. 152 140 3, 220 149 3. 430 6.4 315 0. 145 0.05 143 3, 290 154 3, 5 7. 7 it? 3335 it 151% ill it;

. 0.25 4 Nickel wrbmyl 430 0. 29 0. 10 144 3, 310 161 a, 700 12. 5 4300.725 0. 145 3, 340 167 3. 850 15. 2 as 13% it? 12st 2-? 0 methyl lead lI 430 2.0 t 1.28 145 a. 340 139 3, 200 -4. 1 430 0. 57 0. 06 148 3, 400149 3, 430 0. 7 750 1. 91 0. 20 118 2, 720 117 2, 690 -0. 8 Cobaltnaptheuate (N ate 1) (Note 2) 430 1. 91 O. 20 144 3. 310 145 3, 340 0. 7430 4. 76 0. 50 145 3. 340 138 3. 170 -4. 8 430 4. 75 1. 35 145 3, 340No data (nozzle 0 ogging) Iron pentacarbonyl 430 2. o 0. 57 145 3, 340121 2. 780' --16. 5 430 0. 5 0. 14 145 3, 340 146 3, 360 0. 7 CarbonDisulphide 430 2.0 145 3, 340 145 3, 340 0 Ferrocene 315 0.2 NoData-wonld not run 430 0. 17 No Do. a-would not run Chromium acetylacetonate 315 139 I 35% h 533 I 6 Water 430 0.25 145 3,340 145 3,340 I 0Norm 1.Nuodex cobalt napthenate with solvent, 10.5% cobalt by welght.No'rn 2.150 lb. thrust chamber. All other chambers producedapproximately 4011). thrust.

and chromium, when dissolved in normal propyl nitrate, do not promotethe decomposition of the fuel. From the data of Table I, thedecomposition actually appears to be inhibited as shown by decreases inspecific impulse when salts of these metals are added to the normalpropyl nitrate.

Standard parameters used to measure rocket perform: ance and mentionedin the text and Table 1 are defined as follows in Table 11 below:

7 Table II (1) Specific impulse as determined by thrust- Specificimpulse=thrust/fuel flow (2) Specific impulse as determined from chamberpressure where P =chamber pressure f =exhaust nozzle throat area W=fuelflow Cp=thf1l$t coefi'icient expressed by t=nozzle divergencecoeflicient C =nozzle discharge coefiicient =velocity coefficient P=ambient atmospheric pressure P =combustion chamber pressure =ratio ofspecific heats (3) Characteristic velocity, C*, as determined fromchamber pressure and fuel flow-- where P =chamber pressure f =exhaustnozzle throat area g=gravitational constant W=fuel fiow rate Thetheoretical C* may be expressed by the equation where v=ratio ofspecific heats g=gravitational constant R=universal gas constantT=combustion chamber temperature M =average molecular weight By.utilizing my invention, smaller combustion chambers are required due tothe improvement in the decomposition of propyl nitrate. Hence, lightercombustion chambers may be used, which is particularly advantageous foraircraft.

The invention in its broader aspects is not limited to the specificprocesses and stepsdescribed but departures may be made therefrom withinthe scope of the accompanying claims without departing from theprinciples of the invention and without sacrificing its chiefadvantages.

I claim:

1. An improved monopropellant composition for use in jet propulsiondevices consisting essentially of propyl nitrate and a nickel saltsoluble in said monopropellant and in an amount from about 0.02% toabout 1% by weight calculated as metallic nickel of said propyl nitrate,said nickel salt on decomposition yielding finely divided nickelparticles.

2. An improved monopropellant composition as defined in claim 1 whereinthe soluble nickel salt is an amount from 0.1 to 0.25% by weight of thepropyl nitrate, calculated as metallic nickel.

3. An improved monopropellant composition as define-d in claim 1 whereinthe soluble nickel salt is selected from the group consisting of nickelcarbonyl, nickel acetyl acetonate, nickel diisopropyldithiocarbamate andnickel dinormalpropyldithiocarbamate.

4. An improved monopropellant composition as defined in claim 3, whereinthe soluble nickel salt is nickel carbonyl.

5. An improved monopropellant composition as defined in claim 3, whereinthe soluble nickel salt is nickel acetyl acetonate.

6. An improved monopropellant composition as defined in claim 3, whereinthe soluble nickel salt is nickel diisopropyldithiocarbamate.

7. An improved monopropellant composition as defined in claim 3, whereinthe soluble nickel salt is nickel dinormalpropyldithiocarbamate.

8. A novel method for decomposing propyl nitrate monopropellant in acombustion chamber of a jet propulsion device comprising adding to saidpropyl nitrate outside of the combustion chamber a nickel salt solublein said propyl nitrate and in an amount from about 0.02% to about 1% byweight calculated as metallic nickel of propyl nitrate, passing thepropyl nitrate and soluble nickel salt to the combustion chamber,converting said nickel salt into finely divided nickel particles anddecomposing the propyl nitrate in the presence of said nickel particlesdispersed throughout.

9. The method as defined in claim 8, wherein the soluble nickel salt isadded in an amount from 0.1 to 0.25% by weight of the propyl nitratecalculated as metallic nickel.

10. The method as defined in claim 8, wherein the soluble nickel salt isselected from the group consisting of nickel carbonyl, nickel acetylacetonate, nickel diisopropyldithiocarbamate and nickeldinormalpropyldithiocarbamate.

11. The method as defined in claim 10, wherein the soluble nickel saltis nickel carbonyl.

12.-The method as defined in claim 10, wherein the soluble nickel saltis nickel acetyl acetonate.

13. The method as defined in claim 10, wherein the soluble nickel saltis nickel diisopropyldithiocarbamate.

14. The method as defined in claim 10, wherein the soluble nickel saltis nickel dinormalpropyldithiocarbamate.

References Cited in the file of this patent UNITED STATES PATENTSBartleson et al. July 17, 1951 Doumani et al. July 14, 1953 Maisner Oct.5, 1954 OTHER REFERENCES Chemical & Engineering News, vol. 26, No. 39,Sept.

27, 1948, pages 2892, 2893.

8. A NOVEL METHOD FOR DECOMPOSING PROPYL NITRATE MONOPROPELLANT IN ACOMBUSTION CHAMBER OF A JET PROPULSION DEVICE COMPRISING ADDING TO SAIDPROPYL NITRATE OUTSIDE OF THE COMBUSTION CHAMBER A NICKEL SALT SOLUBLEIN SAID PROPYL NITRATE AND IN AN AMOUNT FROM ABOUT 0.02% TO ABOUT 1% BYWEIGHT CALCULATED AS METALLIC NICKEL OF PROPYL NITRATE, PASSING THEPROPYL NITRATE AND SOLUBLE NICKEL SALT TO THE COMBUSTION CHAMBER,CONVERTING SAID NICKEL SALT INTO FINELY DIVIDED NICKEL PARTICLES ANDDECOMPOSING THE PROPYL NITRATE IN THE PRESENCE OF SAID NICKEL PARTICLESDISPERSED THROUGHOUT.